Broadcasting system using ultrashort waves



Sept. 11, 1934. SCHRUTER 1,973,296

BROADCASTING SYSTEM USING ULTRASHORT WAVES Filed April 5, 1930 INVENTORFRITZ SCHROTER ATTORNEY r atented Sept. 11, 1934 more .Wuamu. l mam,-Hi.

BROADCASTING SYSTEM USING ULTRA- SHDRT WAVES Fritz Schriiter, Berlin,

Telefunken Germany, assignor to Gesellsohaft fiir Drahtlose Telegraphicin. b. H., Berlin, Germany, a corporation of Germany Application April5, 1930, Serial No. 441,975 In Germany April 24, 1929 6 Claims.

The ooject of the present invention is to provide method of andapparatus for acoustic and tical broadcasting wherein there are utilized.ves of order of one meter or decimeter, said wave energy beingquasi-optical in nature. Since the propagation of these waves isrectilinear, the

of the radiator is confined to its optical visi- The invention is basedupon this fact and scloses ways and means adapted to economiutilize abroadcasting station operating in Wave-length range.

The chief idea resides in largely precluding 'iation outside the coneor-solid angle defined c; the connecting lines and the horizon so that 2energy as is radiated will be confined and hill ed to the useful solidangle, this being made possible by the fact that waves of one meter orone decimeter length can be concentrated into sharp beams by structuresof limited dimensions and low cost of plant. The arrangements requiredthe idea into practice, fundamentally speaking, are the same as forlonger waves and directional radiation; for instance, they may conist offinality of dipoles fed under proper has relations. In the case of wavesof an order f o decimeter, it is more advantageous to have curse tocurved reflectors whose surfaces made om metal plate or gauze produce aconcentrator focusing action satisfying the laws of geo- --trical on cs.ihc chief sense of radiation ally be parallel to the horizontal line.ater the altitude of the transmitter above the ground and above itssurroundings, the more ay the vector of maximum intensity be inclined inrotation to the horizontal towards the earth, c more favorable willbecome the angular 'buticn of the radiation attainable with limiteneans.

hows the fundamentals of the method. 1 denotes the transmitter sendingout radiations all directions of the compass, 2 its geometric .l doptical horizon which at the same time imits the practical receivingrange. According to this invention, the radiation is concentrated in thevertical section inside the solid angle or cone denoted by a so that,under ideal conditions, no energy is dissipated in the other solid angledesignated by c. This is made possible by dipoles superposed verticalsense and oscillating under co-phasic conditions in a way well knownfrom short-wave Work. However, for sending out shorter waves, say, of anorder of one decimeter, a reflector i, Fig. 2, presenting rotationalsymmetry may be used, said reflector being conceived as generated byrotating a parabola about its di- PM c:

rectrix 2 as axis. The focal line 3 of the said reflector is studdedwith a rim of dipoles fed with radio frequency energy, 4, 5, to 11, sothat the desired radiation results in being. fairly uniform in alldirections-though being form-ed by a marked beam in vertical elevation.The outline of the beam in this section will be so much more precise,the wider the parabola embracing the radiators, and the greatertherefore the aperture of the reflector. It is possible to mount aplurality of such transmitters above one another. If the dipoles areexcited by means of spark-dis charges (Hertz osciliators) there will beproduced intermittent markedly damped wave-trains so that the chances ofinterference liabl to result in undesirable directive actions, that isto say, zones of different field intensity in the receiving field of thetransmitter will be, practically speaking, absent. Inclination of thevector of the chief radiation towards the horizontal line can beobtained by ce-f cussing the dipole radiators, though moreadvantageously, as shown in Fig. 3, by'a reflector 1 which results byrotating parabola Zabout an axis 4 being slightly oblique in relation toits directrix. 0 Stations of the kind heredisclosed may be received bymeans of nonieotional, though more advantageously the aid directionallyacting, receivers. In order that the incoming energy, apart from the useof con-den er reflec- .tors, may be further concentrated and intensifiedby further concentration of the outgoing radiations, recourse may be hadin many instances to the production of a beam effect in the horizontalcross-sectional plane in addition to that in the verticalcross-sectional plane. This scheme has much to recommend itself, forinstance, in cases where the transmitterv is not situated the center ofthe district to be served, but outside the same. In that case,transmission is substantially confined to the angle of vision formedbetween the territory in question and the origin of the radiation. Butif the transmitting station is located at or near the center of thebroadcasting zone, then supplementary bunching with in the horizontalsection is recommendable for the following reason: In the case ofWave-lengths as here dealt with, it is diilicult to increase the energyproduced in the form of radio frequency in an oscillator tube or aspark-gap to any de- 105 sired extent. On the other hand, paralleling ofsuch generators and feeding the output thereof to an antenna giving offradiations in all directions is mostly prohibitive because of the conduotor and tube capacities associated therewith. 110,;

However, on account of the comparative simplicity and cheapness of plantand installation according to this invention, it would be altogetherfeasible from an economic viewpoint to mount a circle of transmitters l,2, 3, etc., as shown in Fig. i, each one of which sending out a beamconcentrated inside a certain angle a. The result thus is a fan ofbeams, and the intensified aggregate energy thus given off all aroundresults in correspondingly raised field intensities;

If the undamped oscillations given off by the different radiators differby certain frequency values, no danger of disturbing interference willbe produced in the overlap zones a. In this connection periodicfrequency variations of relatively small valueiwobbling so-called) maybe produced.

The same practical result is obtainedwhen the waves are subject tomarked damping owing to spark generation. In that case also, nointerference is noticeable, especially if the feed frequency of thespark-gap in turn is subjected to wobbling.

The distribution of the radiation density inside the angle of the beamis suitably so chosen in the vertical section that it will be greater inthose cones which reach receiving points located at greater distancesthan for those incident in the neighborhood of the transmitter. In thismanner, the receiving problem can be solved to greatest advantage froman economic viewpoint, and the quality of reception in the marginalregions reached by the transmitter will be improved. I

I claim:

1. In an ultrashort wave broadcasting arrange-- ment for propagatingelectromagnetic wave energy through space, said wave energy beingquasi-optical in nature, the combination with a plurality of radiatingunits arranged substantially on a circle and at an appreciable heightabove the earths surface, of reflecting means for said units arranged toconcentrate the radiant energy within a cone formed by the point oftransmission as an apex and a family of lines tangent to the earthssurface.

2. An arrangement for broadcasting over a wide angular sectorelectromagnetic waves of the order of one meter or less in wave lengthcomprising a plurality of highly directional transmitter units emittingsimultaneously beams of different waves of said order of magnitude eachof said beams being within a relatively small angle, the sides of saidangles being arranged to overlap, said units being placed adjacent oneanother and in such fashion that the simultaneously emitted beams areprojected substantially inside the transmitter horizon and supplementeach a other so that a desired wide angular area has propagated throughit electromagnetic wave energy of a wave length of said order ofmagnitude.

3. An arrangement for broadcasting over a wide angular sectorelectromagnetic waves of the order of one meter or less in wave lengthcom-- prising a plurality of highly directional transmitter unitsarranged on a circle and emitting simultaneously beams of differentwaves of said order of magnitude each of said beams being Within arelatively small angle, the sides of said angles being arranged tooverlap, each of said units having a reflector and being placed adjacentto another in such fashion that the simultaneously emitted beams areprojected substantially inside thetransmitter horizon and supplementeach other so that a desired wide angular area has propagated through itelectromagnetic wave energy of a wave length of said order of magnitude.

4. An arrangement for broadcasting over a wide angular sectorelectromagnetic waves of the order of one meter or less in wave length,com prising a plurality of directional transmitter units, emittingsimultaneously beams of waves of said order of magnitude, each of saidbeams covering an angle less than a right angle, the sides of saidangles beingarranged to overlap, said units being spaced adjacent oneanother and in such fashion that the simultaneously emitted beams areprojected substantially inside the transmitter horizon and supplementeach other so that a desired wide angular area has propagated through itelectromagnetic energy of a wave length of said order of magnitude.

5. An arrangement for broadcasting o" a wide angular sectorelectromagnetic waves of the order of one meter or less in wave length,comprising a plurality of directional transm tter units, emittingsimultaneously a fan of beams of waves of said order of magnitude, eachof said units emitting a beam of waves covering a well defined angle,said units being placed adjacent one another and in such fashion thatthe simultaneously emitted waves are projected substantially inside thetransmitter horizon and supplement each other so that a'desired wideangular area has propagated through it electromagnetic energy of a wavelength of said orderof magnitude.

6. In an ultrashort wave transmitter arrangement forpropagatingelectromagnetic wave energy through space, said wave energy beingquasioptical in nature, the combination with a plurality of radiatingunits arranged substantially on a circle and above the earths surface,each of said units emitting a beam of ultrahigh frequency waves coveringan angle less than a right angle, of reflecting means for said unitsarranged to concentrate the radiant energy substantially within a coneformed by the point of transmission as an apex and a family of linestangent to the earths surface.

